1. Field of the Invention
This invention relates in general to electric submersible pumps (ESPs) and, in particular, to a gas separator with improved flow path efficiency.
2. Brief Description of Related Art
Electric submersible pump (ESP) assemblies are disposed within wellbores and operate immersed in wellbore fluids. The ESP assemblies generally include a pump portion and a motor portion. Generally, the motor portion is downhole from the pump portion, and a rotatable shaft connects the motor and the pump. The rotatable shaft may be one or more shafts operationally coupled together. The motor rotates the shaft that, in turn, rotates components within the pump to lift fluid through a production tubing string to the surface. The ESP assembly may also include one or more seal sections coupled to the shaft between the motor and pump. In some embodiments, the seal section connects the motor shaft to the pump intake shaft. The seal section provides an area for the expansion of the ESP motor oil volume, equalizes the internal unit pressure with the wellbore annulus pressures, isolates the clean motor oil from wellbore fluids to prevent contamination, and supports the pump shaft thrust load.
In some embodiments, the ESP assembly includes a gas separator positioned between the seal section and the pump section. ESPs are designed to handle liquid and will suffer from head degradation and gas locking in the presence of a high percentage of free gas. The gas separator is installed at the intake of the pump section, between the seal section and the pump section. Wellbore fluid enters the gas separator and passes through the gas separator into the pump intake. The wellbore fluid is rotated within the separator, centrifugally separating heavier wellbore fluid from lighter wellbore fluid. Generally, heavier wellbore fluid corresponds with fluid that has a lower gas content, and lighter wellbore fluid corresponds with fluid having a higher gas content. The gas separator then directs the heavier wellbore fluid to the pump section intake and the lighter wellbore fluid back into the annulus of the casing. The flowpath of the lighter fluid generally must make a sharp right-angle turn to exit the gas separator and flow back into the casing annulus. The sharp right angle turn causes an increase in the fluid pressure where the lighter wellbore fluid must make a rapid change in momentum to exit, the separator. This coincides with a change in momentum from a path moving circularly uphole and radially inward to a path moving normal to the previous circular path. This pressure increase causes a notable increase in the amount of pumping head needed within the separator chamber. Thus, there is a need for a gas separator within an improved fluid flowpath to increase the efficiency of the overall ESP assembly.